This invention relates to improvements in disk drive systems and, more particularly, to an improved drive arrangement for a flexible magnetic disk.
Recently developed flexible magnetic disks, which comprise a convenient and low cost information storage media, are finding an increasing variety of applications. Typically, each disk is housed in a flat cartridge in which it rotates. Various drive systems have been developed to rotate the disk at a uniform speed about a precise axis. In use, the cartridge is held stationary while the disk is rotated therein, with its rotating surface being accessible through a radial slot in the cartridge.
A portion of a typical flexible disk drive system is disclosed in U.S. Pat. No. 3,768,815 which shows a hub coupled to a drive shaft and wherein the hub has annular inner walls which define an annular recess and a flat face portion. Also included is a rotatable expandable collet and wedging means. The function of the latter is to expand the collet against the hub so as to clamp a central annular portion of the flexible magnetic disk between the flat face portion of the hub and the collet. Thus, as the hub rotates, the clamped disk rotates therewith at the same speed.
In known prior art flexible magnetic disk drive systems, the hub shaft is indirectly coupled to a driving motor. The indirect coupling is generally achieved by the utilization of gears and/or different belt-pulley arrangements which serve to couple the driving motor shaft to the hub shaft and to reduce the hub shaft speed to a desired value, typically 360 rpm. The indirect coupling of the hub shaft to the driving motor increases the system's complexity and cost. Generally AC driving motors, e.g. synchronous motors, are used due to the fact that their output speeds do not vary as a result of appreciable changes of input voltage or load. Due to the different voltage and frequency standards throughout the world, however, a given drive system using one of these motors, built for use in one part of the world, may have to be modified for use in a different part of the world with different voltage and frequency standards.